Reduction of NADP in cyclic photophosphorylation

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SUMMARY

The discussion centers on the mechanism of cyclic photophosphorylation and the reduction of NADP. In cyclic photophosphorylation, electrons from photosystem I are excited by photons and travel through electron acceptors, losing energy. This energy is utilized to reduce NADP to NADPH, despite the absence of hydrogen gain from photolysis. The process supports photoautotrophs in the Calvin cycle, even though true NADPH + H+ is not produced in cyclic photophosphorylation.

PREREQUISITES
  • Understanding of photosynthesis, specifically the roles of photosystem I and II.
  • Knowledge of electron transport chains and their function in energy transfer.
  • Familiarity with the Calvin cycle and its requirements for NADPH.
  • Basic concepts of photophosphorylation and proton motive force (PMF).
NEXT STEPS
  • Research the differences between cyclic and non-cyclic photophosphorylation.
  • Learn about the role of NADPH in the Calvin cycle and how it is generated.
  • Investigate specific plant species that utilize only cyclic photophosphorylation.
  • Explore the mechanisms of proton gradient establishment in photosynthetic organisms.
USEFUL FOR

Students of plant biology, biochemists, and educators seeking to deepen their understanding of photosynthetic processes and the intricacies of cyclic photophosphorylation.

PWiz
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I understand that an electron jumps to an excited state after absorbing a photon with the right energy (frequency) in photosystem 1 and exits the structure of the primary pigment, moves through different electron acceptors and returns to photosystem 1 (now at a lower energy state). What I don't understand is why NADP gets reduced using the energy the electron lost while moving between electron acceptors. Gain of electrons corresponds to reduction, but surely the electron returns back to the photosystem, and is not incorporated into NADP? How can reduced NADPH be formed if there is no hydrogen gain either (since photolysis does not occur in cyclic photophosphorylation)? If NADPH is not formed, then how do photoautotrophs that only use cyclic photophosphorylation perform the Calvin cycle (and produce a carbohydrate)?
 
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true NADPH +H+ is not formed in cyclic photophosphorylation but..
i'm a bit unaware as to which plant performs ONLY cyclic photophosphorylation ...could you please tell me that...because the whole reason for evolution to bring in cyclic phosphorylation was to support non-cyclic with setting up the proton gradient (PMF)
 

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